This invention relates to an improved process for the preparation of benzoyl halides and meta-halosulfonylbenzoyl halides and, more particularly, to such process involving the reaction of benzotrihalide with oleum.
Benzoyl halides and chlorosulfonylbenzoyl halides are well known in the chemical industry and have been employed in as intermediates for a variety of known and useful end products. Benzoyl halides, are highly reactive acid halides, useful in a variety of reactions to introduce the benzoyl group into organic compounds, especially through Friedel-Crafts reactions. Benzoyl halides are employed in the preparation of perfumes, pharmaceuticals, dyes, resins and pesticides. Similarly, halosulfonylbenzoyl halides are known to be useful for a variety of purposes and have been employed, for example, as polymerization catalysts and as intermediates in the preparation of pharmaceuticals and azo dyes. In addition, meta-halosulfonylbenzoyl halides, may be desulfonylated in a known manner to prepare m-halobenzoyl halides, which, in turn, are useful for various purposes in the chemical industry, including, for example, as chemical intermediates for the preparation of dyes; pharmaceuticals; agricultural chemicals; as well as various other organic chemical end products.
Various methods for the preparation of benzoyl halides or meta-sulfonylbenzoyl halides are known in the art. It is known, for example, from U.S. Pat. No. 3,691,217, that benzoyl chlorides and benzaldehydes may be produced by reacting benzo polychloromethanes, such as benzotrichloride, with an organic carboxylic acid in the presence of a tin chloride catalyst.
U.S. Pat. No. 3,290,370, to Weil and Lisanke, disclose the preparation of m-chlorosulfonylbenzoyl chloride by reaction of benzotrichloride with chlorosulfonic acid. The stoichiometry of the reaction is such that, even under ideal conditions, for each mole of desired product, two moles of mineral acid are produced, with the need for disposal thereof. In addition, to obtain high yields of the desired m-chlorosulfonylbenzoyl chloride, substantial excess of the chlorosulfonic acid is employed, presenting additional problems of separation, and disposal or recycling thereof.
U.S. Pat. No. 3,322,822 to Gelfand, discloses the preparation of m-chlorosulfonylbenzoyl chloride by reaction of benzotrichloride and sulfur trioxide. With the use of substantial excess of sulfur trioxide reactant, yields of m-chlorosulfonylbenzoyl chloride as high as 65% are shown to be obtainable.
Although the prior art provides a variety of processes for the preparation of either benzoyl halides or halobenzoylsulfonyl halides, it will be appreciated that still further improvements in efficient utilization of reactants is desirable as well as improvements in the yield of the meta-isomer of halosulfonylbenzoyl halide obtainable.
Accordingly, it is an object of this invention to provide an improved process for the preparation of halosulfonylbenzoyl halides wherein the meta-isomer thereof may be selectively produced in high yields. It is a further object to provide a process for the preparation of co-products, benzoyl halides and halosulfonylbenzoyl halides wherein the proportional yield of each may be controllably varied.